全文获取类型
收费全文 | 18114篇 |
免费 | 1585篇 |
国内免费 | 697篇 |
专业分类
电工技术 | 627篇 |
技术理论 | 1篇 |
综合类 | 1219篇 |
化学工业 | 3169篇 |
金属工艺 | 4224篇 |
机械仪表 | 648篇 |
建筑科学 | 904篇 |
矿业工程 | 1625篇 |
能源动力 | 337篇 |
轻工业 | 674篇 |
水利工程 | 117篇 |
石油天然气 | 277篇 |
武器工业 | 91篇 |
无线电 | 303篇 |
一般工业技术 | 1657篇 |
冶金工业 | 4250篇 |
原子能技术 | 111篇 |
自动化技术 | 162篇 |
出版年
2024年 | 53篇 |
2023年 | 175篇 |
2022年 | 451篇 |
2021年 | 498篇 |
2020年 | 485篇 |
2019年 | 409篇 |
2018年 | 397篇 |
2017年 | 461篇 |
2016年 | 644篇 |
2015年 | 592篇 |
2014年 | 999篇 |
2013年 | 1075篇 |
2012年 | 1199篇 |
2011年 | 1275篇 |
2010年 | 936篇 |
2009年 | 822篇 |
2008年 | 689篇 |
2007年 | 1058篇 |
2006年 | 1090篇 |
2005年 | 917篇 |
2004年 | 828篇 |
2003年 | 792篇 |
2002年 | 751篇 |
2001年 | 635篇 |
2000年 | 545篇 |
1999年 | 418篇 |
1998年 | 377篇 |
1997年 | 327篇 |
1996年 | 290篇 |
1995年 | 254篇 |
1994年 | 212篇 |
1993年 | 139篇 |
1992年 | 142篇 |
1991年 | 88篇 |
1990年 | 100篇 |
1989年 | 75篇 |
1988年 | 57篇 |
1987年 | 30篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 17篇 |
1983年 | 5篇 |
1982年 | 19篇 |
1981年 | 11篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
为了研究鞣酸铁催化剂对固体推进剂中常见组分热分解性能的影响,采用超声喷雾干燥法制得三种亚微米复合微球(鞣酸铁(Ta-Fe)/六硝基六氮杂异伍兹烷(CL-20)、鞣酸铁/黑索今(RDX)、鞣酸铁/奥克托今(HMX))。利用扫描电镜(SEM)和粒度分析等方法分别对复合微球的形貌、粒度和组分进行表征。采用差示扫描量热法(DSC)研究复合微球中鞣酸铁对CL-20、RDX、HMX热分解的催化过程及动力学参数的影响。结果表明,鞣酸铁分布均匀,样品均呈球状颗粒,且流散性好,粒度为500~1000 nm;鞣酸铁能有效促进CL-20、RDX、HMX的热分解,使得CL-20、RDX、HMX的热分解峰温分别提前了17.2,8.2,11.5℃,其中鞣酸铁对CL-20的热分解催化效果最佳,Ta-Fe/CL-20复合微球的活化能与原料CL-20相比降低了9.6 kJ·mol……-1。 相似文献
92.
为获得高强度高塑性的球墨铸铁,通过加入微量合金元素 Mn 和 Cu,研究 Mn 和 Cu 对球墨铸铁微观组织和力学特性的影响。结果表明:Mn 的加入提高了球墨铸铁中珠光体含量、球墨铸铁的抗拉强度和硬度,但塑性下降;在 Mn 含量一定时,添加适量的 Cu 后,球墨铸铁的性能进一步提高。研究发现,添加适量的合金元素 Mn 和 Cu 可生产高强度的球墨铸铁,且塑性值比对应的国家标准大幅度提高。 相似文献
93.
介绍了HT250灰口铸铁的机械性能、热处理工艺和铸造结构,阐述了铸造零件的结构优化措施和热处理工艺措施。通过应用实例的分析和验证,获得HT250灰口铸铁在电子工业专用设备中的重要用途;HT250灰口铸铁是一种重要的材料,深入研究其性能,可使其广泛地应用于设备制造行业。 相似文献
94.
自从上世纪80年代以来,经过不断的改善创新,我国的冶金电气自动化控制技术获得迅速的发展,全部冶金过程基本已经实现了自动化,这显然是一项伟大的成就。本文阐述了该技术的的最近的创新与突破,并以钢铁冶炼为基础探析了应用该技术的环保问题,在此基础上预测了本技术的未来发展的潜力。 相似文献
95.
96.
《Journal of Visual Communication and Image Representation》2014,25(5):978-993
In this paper, we propose an adaptive and accurate moving cast shadow detection method employing online sub-scene shadow modeling and object inner-edges analysis for applications of static-camera video surveillance. To describe shadow appearance more accurately, the proposed method builds adaptive online shadow models for sub-scenes with different conditions of irradiance and reflectance. The online shadow models are learned by utilizing Gaussian functions to fit the significant peaks of accumulating histograms, which are calculated from Hue, Saturation and Intensity (HSI) difference of moving objects between background and foreground. Additionally, object inner-edges analysis is adopted to reject camouflages, which are misclassified foreground regions that are highly similar to shadows. Finally, the main shadow regions are expanded to recycle the misclassified shadow pixels based on local color constancy. The proposed algorithm can adaptively handle the shadow appearance changes and camouflages without prior information about illuminations and scenarios. Experimental results demonstrate that the proposed method outperforms state-of-the-art methods. 相似文献
97.
Thin films of Fe and Cu-codoped CdO (CdO:Cu:Fe) with different Fe content and fixed Cu content were deposited in a high vacuum on glass and Si wafer substrates. These films were studied by X-ray fluorescence (XRF), X-ray diffraction (XED), optical spectroscopy, and dc-electrical measurements. The structural results show enhancement of film [1 1 1] orientation with Fe doping especially with 1.3%Fe film. Also, light doping with Fe improves the dc-conduction parameters of the CdO:Cu:Fe films so that the utmost enhancement of mobility (90.5 cm2/Vs) and conductivity (1470.6 S/cm) was found with 1.3 wt% Fe doping level. It was found that the variation in the bandgap is related to the variation in electron concentration that caused by Fe doping. For low Fe ion concentration (<1.3 wt% ), the bandgap varies according to the Moss–Burstein model. 相似文献
98.
Ferroelectric and Magnetic Properties in Room‐Temperature Multiferroic GaxFe2−xO3 Epitaxial Thin Films 下载免费PDF全文
Tsukasa Katayama Shintaro Yasui Yosuke Hamasaki Takahisa Shiraishi Akihiro Akama Takenori Kiguchi Mitsuru Itoh 《Advanced functional materials》2018,28(2)
GaFeO3‐type iron oxide is a promising room‐temperature multiferroic material due to its large magnetization. To expand its usability, controlling the ferroelectric and magnetic properties is crucial. In this study, high‐quality GaxFe2–xO3 (x = 0–1) epitaxial films are fabricated and their properties are systematically investigated. All films exhibit room‐temperature out‐of‐plane ferroelectricity, showing that the coercive electric field (Ec) decreases monotonically with x. Additionally, the films show in‐plane ferrimagnetism with a Curie temperature (TC) >350 K at x = 0–0.6. The coercive magnetic field (Hc) decreases with x at x ≤ 0.6, but shows a constant value at x > 0.6, whereas the saturated magnetization (Ms) increases with x at x ≤ 0.6, but decreases with x at x > 0.6. X‐ray magnetic circular dichroism reveals that the large magnetization at x = 0.6 is derived from Fe3+ (3d5) at octahedral sites. The controllable range of the Ec, Hc, and Ms values at room temperature (400–800 kV cm?1, 1–8 kOe, and 0.2–0.6 µB/f.u.) is very wide and differs from those of well‐known multiferroic BiFeO3. Furthermore, the GaxFe2?xO3 films exhibit room‐temperature magnetocapacitance effects, indicating that adjusting TC near room temperature is useful to achieve large room‐temperature magnetocapacitance behavior. 相似文献
99.
100.
Comparative Study of 10-MW High-Temperature Superconductor Wind Generator with Overlapped Field Coil Arrangement 下载免费PDF全文
The electromagnetic characteristics and iron loss of a high-temperature superconductor wind generator (HWG) equipped with an overlapped field coil arrangement (OFCA) are studied by comparing with the one equipped with the conventional field coil arrangement (CFCA). Through a quantitative analysis, it was found that HWG with OFCA exhibits better electromagnetic characteristics than HWG with CFCA and can reduce the iron loss by eliminating the magnetic flux sag caused by the adjacent field coil sides with the same current flow direction. In addition, the OFCA topology can further reduce the volume of the wind generator. 相似文献